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Journal of the Chinese Medical... Aug 2015From a hemodynamic point of view, hepatic vascular resistance and portal inflow determine the level of portal pressure. Factors that determine hepatic vascular... (Review)
Review
From a hemodynamic point of view, hepatic vascular resistance and portal inflow determine the level of portal pressure. Factors that determine hepatic vascular resistance include both structural and dynamic components. Among the structural components are histological characteristics such as steatosis, fibrosis, regeneration nodules, and neo-angiogenesis. Dynamic structures include cells with contractile properties such as hepatocytes, hepatic stellate cells, sinusoidal endothelial cells, and Kupffer cells. The contributions of the interactions between four cells in cirrhotic livers resulted in hepatic endothelial dysfunction, hepatic microcirculatory dysfunction, hepatic venous dysregulation, hepatic fibrogenesis, and subsequently increased intrahepatic resistance and portal hypertension in cirrhosis. The pathogenic mechanisms that trigger the associated abnormalities in hepatic microcirculations include persistent endotoxemia, increased hepatic oxidative stress, activated endocannabinoids substances, pathogenic sinusoidal remodeling, and hypoperfusion in cirrhotic livers. Cumulative data suggested that various therapeutic strategies targeting hepatic microcirculation provided effective improvement of the systemic abnormalities of cirrhosis. Accordingly, the mechanistic and therapeutic approaches focusing on the disarrangement of hepatic microcirculation will be introduced in this article.
Topics: Bacterial Translocation; Endocannabinoids; Fibroblast Growth Factor 2; Humans; Liver Circulation; Liver Cirrhosis; Microcirculation; Nitric Oxide; Vascular Endothelial Growth Factor A
PubMed: 26074366
DOI: 10.1016/j.jcma.2015.05.005 -
Experimental Eye Research May 2024The retinal microcirculation system constitutes a unique terminal vessel bed of the systemic circulation, and its perfusion status is directly associated with the neural... (Review)
Review
The retinal microcirculation system constitutes a unique terminal vessel bed of the systemic circulation, and its perfusion status is directly associated with the neural function of the retina. This vascular network, essential for nourishing various layers of the retina, comprises two primary microcirculation systems: the retinal microcirculation and the choroidal microcirculation, with each system supplying blood to distinct retinal layers and maintaining the associated neural function. The blood flow of those capillaries is regulated via different mechanisms. However, a range of internal and external factors can disrupt the normal architecture and blood flow within the retinal microcirculation, leading to several retinal pathologies, including diabetic retinopathy, macular edema, and vascular occlusions. Metabolic disturbances such as hyperglycemia, hypertension, and dyslipidemia are known to modify retinal microcirculation through various pathways. These alterations are observable in chronic metabolic conditions like diabetes, coronary artery disease, and cerebral microvascular disease due to advances in non-invasive or minimally invasive retinal imaging techniques. Thus, examination of the retinal microcirculation can provide insights into the progression of numerous chronic metabolic disorders. This review discusses the anatomy, physiology and pathophysiology of the retinal microvascular system, with a particular emphasis on the connections between retinal microcirculation and systemic circulation in both healthy states and in the context of prevalent chronic metabolic diseases.
Topics: Humans; Microcirculation; Retinal Vessels; Metabolic Diseases; Retinal Diseases; Regional Blood Flow
PubMed: 38574944
DOI: 10.1016/j.exer.2024.109885 -
Interventional Cardiology Clinics Jan 2023Ischemic heart disease (IHD) affects more than 20 million adults in the United States. Although classically attributed to atherosclerosis of the epicardial coronary... (Review)
Review
Ischemic heart disease (IHD) affects more than 20 million adults in the United States. Although classically attributed to atherosclerosis of the epicardial coronary arteries, nearly half of patients with stable angina and IHD who undergo invasive coronary angiography do not have obstructive epicardial coronary artery disease. Ischemia with nonobstructive coronary arteries is frequently caused by microvascular angina with underlying coronary microvascular dysfunction (CMD). Greater understanding the pathophysiology, diagnosis, and treatment of CMD holds promise to improve clinical outcomes of patients with ischemic heart disease.
Topics: Adult; Humans; Microcirculation; Coronary Artery Disease; Microvascular Angina; Coronary Angiography
PubMed: 36372455
DOI: 10.1016/j.iccl.2022.09.010 -
British Journal of Anaesthesia Sep 2015Cardiovascular resuscitation is a cornerstone of critical care practice. Experimental advances have increased our understanding of the role of the microcirculation in... (Review)
Review
Cardiovascular resuscitation is a cornerstone of critical care practice. Experimental advances have increased our understanding of the role of the microcirculation in shock states and the development of multi-organ failure. Strategies that target the microcirculation in such conditions, while theoretically appealing, have not yet been shown to impact upon clinical outcomes. This review outlines the current understanding of microcirculatory dysfunction in septic, cardiogenic, and hypovolaemic shock and outlines available treatments and strategies with reference to their effects upon the microcirculation.
Topics: Critical Care; Humans; Microcirculation; Resuscitation; Shock
PubMed: 26269467
DOI: 10.1093/bja/aev163 -
Shock (Augusta, Ga.) Apr 2019The conjunctival region may serve as an alternative site for microcirculatory measurements. The present study was performed to investigate the correlation of sublingual...
INTRODUCTION
The conjunctival region may serve as an alternative site for microcirculatory measurements. The present study was performed to investigate the correlation of sublingual and conjunctival microcirculation in ovine models of septic and hemorrhagic shock.
METHODS
Septic shock was induced in 10 sheep by inoculation of feces into the peritoneal cavity until mean arterial pressure (MAP) was <60 mm Hg and arterial lactate level was ≥1.8 mmol· L. In another 10 sheep, hemorrhagic shock was induced by stepwise blood withdrawal of 3×10 mL·kg. Systemic hemodynamics and parameters of blood gas analysis were analyzed. Conjunctival and sublingual microcirculation were monitored and analyzed according to current recommendations. Parameters were measured at baseline and at shock time.
RESULTS
Septic shock resulted in a significant drop in MAP and cardiac index (CI), and an increase in arterial lactate levels. While the total vessel density (TVD) in the sublingual microcirculation was relatively well maintained, the perfused vessel density (PVD) and the microvascular flow index (MFI) were significantly reduced in septic shock. Hemorrhagic shock reduced MAP and CI, and increased arterial lactate levels. TVD was relatively unchanged in hemorrhagic shock, while PVD and MFI were significantly decreased. The conjunctival microcirculation showed similar changes to the sublingual microcirculation in both models.
CONCLUSIONS
The findings of the current study support the proposed use of the conjunctiva as an alternative site for microcirculatory monitoring in hemorrhagic and septic shock. Further studies should focus on the impact of therapy and the loss of correlation between the different microcirculatory regions in advanced shock.
Topics: Animals; Conjunctiva; Female; Hemodynamics; Microcirculation; Sheep; Shock, Hemorrhagic; Shock, Septic
PubMed: 30199510
DOI: 10.1097/SHK.0000000000001173 -
Journal of Applied Physiology... Mar 2022Extracorporeal membrane oxygenation (ECMO) is a procedure used to aid respiratory function in critical patients, involving extracorporeal circulation (ECC) of blood....
Extracorporeal membrane oxygenation (ECMO) is a procedure used to aid respiratory function in critical patients, involving extracorporeal circulation (ECC) of blood. There is a limited number of studies quantifying the hemodynamic effects of ECC procedures on the microcirculation. We sought to mimic veno-arterial-ECMO flow conditions by use of a scaled-down circuit primed with either lactate Ringer (LR) or 5% human serum albumin (HSA). The circuit was first tested using benchtop runs with blood, and subsequently used for in vivo experiments in Golden Syrian hamsters instrumented with a dorsal window chamber to allow for quantification of microvascular hemodynamics and functional capillary density (FCD). Results showed significant impairment in FCD, and a reduction of arteriolar and venular blood flow, with HSA providing significant higher blood flows and FCD compared with LR. Changes in hematocrit and RBC labeling after ECC reflected a shift in plasma volume, which may stem from a loss in intravascular oncotic pressure due to priming fluids. The distribution of hemoglobin oxygen saturation in the microvasculature showed a significant decrease in venules after ECC. In addition, major organs such as the kidney and heart showed increases in both inflammatory and damage markers. These results suggest that ECC impairs microvasculature function and promotes ischemia and hypoxia in the tissues, which can be vital to understanding comorbid clinical outcomes from ECC procedures such as acute kidney injury and multiorgan dysfunction. ECC reduces microvascular perfusion, with no full recovery 24 h after ECC. HSA performed better as compared with LR in terms of FCD and venule flow, as well as venule oxygen saturation. Increases in inflammatory and damage markers in key organs were observed within all organs analyzed.
Topics: Animals; Capillaries; Cricetinae; Extracorporeal Circulation; Humans; Microcirculation; Microvessels; Oxygen; Perfusion
PubMed: 35085033
DOI: 10.1152/japplphysiol.00726.2021 -
Journal of Cerebral Blood Flow and... Oct 2021The blood-brain barrier (BBB) is dysfunctional in temporal lobe epilepsy (TLE). In this regard, microvascular changes are likely present. The aim of this review is to... (Review)
Review
The blood-brain barrier (BBB) is dysfunctional in temporal lobe epilepsy (TLE). In this regard, microvascular changes are likely present. The aim of this review is to provide an overview of the current knowledge on microvascular changes in epilepsy, and includes clinical and preclinical evidence of seizure induced angiogenesis, barriergenesis and microcirculatory alterations. Anatomical studies show increased microvascular density in the hippocampus, amygdala, and neocortex accompanied by BBB leakage in various rodent epilepsy models. In human TLE, a decrease in afferent vessels, morphologically abnormal vessels, and an increase in endothelial basement membranes have been observed. Both clinical and experimental evidence suggests that basement membrane changes, such as string vessels and protrusions, indicate and visualize a misbalance between endothelial cell proliferation and barriergenesis. Vascular endothelial growth factor (VEGF) appears to play a crucial role. Following an altered vascular anatomy, its physiological functioning is affected as expressed by neurovascular decoupling that subsequently leads to hypoperfusion, disrupted parenchymal homeostasis and potentially to seizures". Thus, epilepsy might be a condition characterized by disturbed cerebral microvasculature in which VEGF plays a pivotal role. Additional physiological data from patients is however required to validate findings from models and histological studies on patient biopsies.
Topics: Blood-Brain Barrier; Epilepsy; Female; Humans; Male; Microcirculation
PubMed: 33866850
DOI: 10.1177/0271678X211010388 -
Best Practice & Research. Clinical... Dec 2016Burn shock is characterized by profound hemodynamic alterations mainly associated with rapid loss of intravascular volume related to severe capillary leak. Thus, fluid... (Review)
Review
Burn shock is characterized by profound hemodynamic alterations mainly associated with rapid loss of intravascular volume related to severe capillary leak. Thus, fluid resuscitation conventionally based on macrocirculatory targets is considered as a corner stone of initial management of patients with burns. Nonetheless, traditional markers such as blood pressure, urinary output, and cardiac output are helpful but do not sufficiently reflect the adequacy of perfusion and oxygenation at the microcirculatory level. Microcirculatory alterations have been identified in patients with severe burns even when macrocirculatory variables are within therapeutic goals. In this review, we discuss the pathophysiology of the microvascular alterations in burn shock, its coherence with macrocirculatory physiologic variables, and potential future implications for the treatment of burn shock.
Topics: Burns; Edema; Fluid Therapy; Hemodynamics; Humans; Microcirculation; Shock
PubMed: 27931647
DOI: 10.1016/j.bpa.2016.10.004 -
Journal of Theoretical Biology Jul 2022We consider the flow of blood, treated as an incompressible Newtonian fluid, through vessels undergoing periodic oscillations. As remarked by many authors, in the...
We consider the flow of blood, treated as an incompressible Newtonian fluid, through vessels undergoing periodic oscillations. As remarked by many authors, in the absence of valves oscillations hinder the flow because of the lumen reduction. The underlying biological mechanism is the so-called vasomotion, observed long ago in small blood vessels. Here, we study the vasomotion in arterioles and provide its theoretical justification by analyzing the effect when the network of vessels downstream of the arterioles is considered. We thus explain both quantitatively and qualitatively, why the oscillations of the arteriole walls, a phenomenon that undoubtedly reduces blood flow at the level of the single arteriole, play a fundamental role in microcirculation. In "large" arterioles we analyze also the coupling between the vasomotion and the Fåhræus-Lindqvist effect (the tendency of the erythrocytes to accumulate towards the center). In particular, we prove that the presence of a cell depleted layer close to the vessel walls mitigates the disadvantage caused by the lumen reduction.
Topics: Arterioles; Erythrocytes; Microcirculation
PubMed: 35429550
DOI: 10.1016/j.jtbi.2022.111124 -
Anesthesiology Dec 2019
Topics: Abdomen; Microcirculation; Mouth Floor; Myocardial Contraction
PubMed: 31567361
DOI: 10.1097/ALN.0000000000002995